Method for diagnosing an impulse line blockage in a pressure trasducer, and pressure transducer

ABSTRACT

A method for the detection of diagnosis of a blockage of an impulse line in a pressure measurement transducer and a corresponding pressure measurement transducer are disclosed, in which at least one characteristic value is compared with at least one reference value for the analysis of at least one measurement signal and, depending on the result of the comparison, an action is triggered, wherein the, or every, characteristic value is produced, with the aid of at least single parameters of a model describing the transmission behavior of impulse lines with which the pressure measurement transducer is coupled to a line traversed by a fluid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2006/007172 filed Jul. 20, 2006 and claims the benefitthereof.

FIELD OF INVENTION

The invention relates to a method for diagnosing an impulse lineblockage in a (pressure) transducer, and a (pressure) transducer whichis prepared and designed for implementing the method. Pressuretransducers are known per se and are designed in particular formeasuring pressure changes at a point of discontinuity, e.g. a so-calledorifice meter, in a pipe through which a liquid or a gas (fluid) flows.Such pressure changes are detected via pressure differences arising atthe orifice meter. Flow rate measurement is also possible on the basisof differential pressure measurement of this kind.

BACKGROUND OF INVENTION

The pressure transducer incorporates, as a sensing element, a pressuresensor which is coupled to a region upstream and downstream of the pointof discontinuity via so-called impulse or differential pressure lines.However, such a coupling may weaken with time, e.g. due to one or moreof the impulse lines becoming blocked (clogging, fouling). In somecircumstances, however, a weakening coupling is detectable bymeasurement signals recorded by the pressure sensor. Insofar as theinvention therefore relates to a method and a corresponding apparatusfor diagnosing an impulse line, i.e. in particular detecting a blockageof one or more impulse lines and/or of deposits on the orifice meter ora diaphragm acting as the interface between the impulse lines and thepressure transducer and/or any diaphragm abrasion, it applies inparticular to a method and a corresponding apparatus for analyzing acharacteristic value relating thereto in respect of a deviation from oraccordance with at least one predefined or predefinable reference value.A weakening or faulty coupling is detectable in this respect e.g. on thebasis of a measure for the accordance of the characteristic value withsuch a reference value or a plurality of such reference values.

Generic methods or devices are generally known. For example, U.S. Pat.No. 5,680,109 discloses using, in addition to a differential pressuretransducer, an additional absolute pressure sensor and comparing anymeasurement noise variance with a reference value. In WO 2001 35174 itis proposed to determine an independent reference signal whosedifference with respect to the measurement signal allows anydeterioration in the quality of the measurement signal to be gauged. Toevaluate the measurement signal, it has been disclosed in U.S. Pat. No.6,532,392 to compare the measurement signal with a predetermined valueof a parameter and to use predefined rules, fuzzy logic or neuralnetworks for the final evaluation. WO 97 36215 discloses determining astatistical parameter of a digitized measurement signal using predefinedrules, fuzzy logic or neural networks and then applying a fuzzymembership function to the statistical parameter. Also, U.S. Pat. No.6,654,697 discloses determining a difference between a digitizedmeasurement signal and the ascertained average value by means of amoving-average algorithm. From this difference, diagnostic data is thendetermined taking current and historical data into account, a traineddata set being calculated from the current and historical data in atraining mode. Finally, it is known from U.S. Pat. No. 6,539,267 tocalculate a statistical parameter such as variance or rate of change bymeans of an algorithm and to generate a trained value by means of amicroprocessor by monitoring the statistical parameter during normaloperation. The trained parameter can be dynamically adapted fordifferent underlying conditions.

Other prior art is described in the following documents: WO 97 48974; JP2004 354280; U.S. Pat. No. 6,397,411; US 2002 029,130; US 2004 068,392;US 2004 204,883; U.S. Pat. No. 6,701,274; U.S. Pat. No. 5,570,300; U.S.Pat. No. 5,675,724; U.S. Pat. No. 5,665,899; U.S. Pat. No. 5,661,668;U.S. Pat. No. 6,047,220; U.S. Pat. No. 5,956,663; U.S. Pat. No.5,828,567 and U.S. Pat. No. 5,495,769.

In an older unpublished application of the same applicant there is alsodisclosed a method and a corresponding apparatus wherein, by means of ananalysis device, at least one characteristic value in respect of the, oreach, measurement signal is determined and the at least onecharacteristic value is compared with at least one predefined orpredefinable reference value. Then, depending on the result of thecomparison, a predefined or predefinable action is initiated. For thispurpose an algebraic function is adapted to the measurement signal bymeans of the analysis device and at least one value of a parameter inrespect of at least one segment of the algebraic function is determinedby means of the analysis device as a characteristic value. Thisapplication can be traced back to the same inventor as the presentapplication and has been submitted under the same title as the presentapplication.

SUMMARY OF INVENTION

The approaches followed according to the prior art are not quite optimuminsofar as they—apart from the above mentioned unpublishedapplication—only take into account a vanishingly small part of thehistory of the measured values obtained respectively, any timefluctuations often even being averaged. As a result of this and due to amathematical processing of the measurement signals that is usuallyprovided, e.g. squaring, important information in respect of the phase,i.e. any time offset between a plurality of measurement signals, islost. Equal history lengths of the measurement signals to be correlatedhave likewise been used; both of length one or two in each case.Correlation of absolute pressure measurement signals also of the highand low pressure side has not been considered. Instead of this, aninstantaneous cross correlation of an absolute pressure measurementsignal with a differential pressure measurement signal or aninstantaneous autocorrelation of individually recorded measurementsignals is taken into account.

An object of the invention accordingly consists in specifying a furtherembodiment for operating a pressure transducer, in particular fordiagnosing an impulse line blockage in a pressure transducer, and acorresponding pressure transducer which in particular avoid theabovementioned disadvantages or at least reduce them in respect of theirrespective effects.

This object is achieved by a method and a apparatus for carrying out themethod according to the claims.

In a method for operating a pressure transducer which is connected by ahigh-pressure and a low-pressure impulse line to a pipe through which afluid flows during operation, wherein a pressure sensor incorporated ina pressure transducer supplies at least one measurement signal andwherein, by means of an analysis device, at least one characteristicvalue relating to the measurement signal is determined, the at least onecharacteristic value is compared with at least one predefined orpredefinable reference value and, depending on the result of thecomparison, a predefined or predefinable action is initiated, or in acorresponding method for diagnosing a blockage in at least one impulseline, the following is provided for this purpose: The pressure sensorsupplies as the measurement signal a first and second measurementsignal. On the basis of the first and second measurement signal,parameters of a model describing a response of the impulse lines aredetermined using the analysis device. The characteristic value providedfor evaluation based on the reference value is produced using at leastindividual parameters of the model.

The operating or diagnostic method is therefore based on the knowledgethat, compared to using comparatively “simple” statistical quantitiessuch as the variance or a two-point correlation, parameters of atransfer function, i.e. of a mathematical relation underlying therespective model, are largely independent of process-induced effects,i.e. instantaneous effects, but highly dependent on the functional stateof the transducer and of individual or a plurality of impulse lines.This knowledge is utilized for the operating method or the diagnosticpossibility encompassed by the operating method in that such modelparameters are determined and a characteristic value designed forevaluating the transducer is derived from one or more of these modelparameters. A calculation (estimation) of model parameters or any otherway of obtaining such model parameters allows, with known geometry,particularly of the impulse lines, and a given model, a quantitativeestimation of the condition of the transducer, the term transducerincluding at least also the impulse lines, namely e.g. of a blockagediameter of the impulse lines or of a settling time of flow ratemeasured value. The measurement signals recorded are used as the basisfor determining the model parameters. In respect of the measurementsignals, the method provides for using at least two measurement signals,so as to satisfactorily take into account the aspect of detecting anytime shifts (phase displacement).

Instead of determining characteristic values without phase informationbetween two signals with extremely short signal length, parameters ofsuitable models for describing the response of the impulse lines aredetermined or estimated. Models of most diverse order, e.g. asecond-order model, come into consideration as models. In addition oralternatively, so-called autoregressive models, AR models, ormoving-average models, MA models, or a combination of the two, ARMAmodels, come into consideration. The relevant model describes arelationship between the two measurement signals, i.e. a differentialpressure measurement signal and an absolute pressure measurement signalor two absolute pressure measurement signals, for example. A structuree.g. of an ARMA model is dependent on the physical effects of the faultto be detected. For online identification of a fault, i.e. a blockage,for example, there is determined, on the basis of the estimated modelparameters, at least one characteristic value which, because of theunderlying model concept, is assigned to a fault type and which permitsa physical interpretation.

An advantage of the invention consists in the better evaluation of theinformation contained in the measurement signals and therefore in aqualitatively improved diagnostic capability. In addition, no test faultneeds to be introduced in order to determine a parameter in the case ofa measuring point fault. Instead, the parameter is determined on thebasis of a predefinable model and geometric variables describing thepressure transducer and/or individual or a plurality of impulse lines ora combination of pressure transducer and the or each impulse line.Moreover, using the estimated model parameters on the basis of theunderlying model as well as known geometric variables such as the lengthof the impulse lines, transducer characteristics, e.g. free diameter ofthe impulse lines or settling speed until correct indication of themeasured value, can be estimated and displayed to an operator.

Another advantage of the invention is that by using transfer models achange in the dynamic response of the impulse lines or of thetransducer, e.g. because of blockages, diaphragm abrasion or deposits,can be detected on the basis of a change in the estimated parameters,e.g. diameter of the impulse lines. The response therefore describes afunctional state of the transducer, said response being to a largeextent independent of the relevant process conditions, so that therespective models and the parameters estimated on this basis are alsolargely independent of such process conditions. In addition, thereexists little uncertainty in respect of the reference value to be usedfor evaluating the or each characteristic value.

A comparison with other methods which were applied to the measurementsignal by a test station has generally shown better results for theapproach according to the invention. The compared methods includeddirect identification of parameters from the measurement signal, such asvariance, mean value, skewness and kurtosis, or from the spectrum of themeasurement signal and a main component correlation analysis.

The approach generally allows impulse line blockages to be detectedlargely independently of the operating conditions and permits aphysically interpretable characteristic value such as the measured valuesettling time or remaining pipe diameter to be specified. This enables areference value to be determined more easily, in some cases withoutexperimental insertion of an artificial blockage. By detecting impulselines blockage, lines can be cleaned when settling of the measured valuetakes longer than events to be measured.

The dependent claims relate to preferred embodiments of the presentinvention. Back-references used in dependent claims relate to furtherembodiments of the subject matter of the main claim by virtue of thefeatures of the particular dependent claim; they are not to beunderstood as a waiver of the right to independent, objective protectionfor the combination of features of the dependent claims to which theyrefer. In addition, having regard to an interpretation of the claims inthe case of a more detailed concretization of a feature in a subordinateclaim, it is to be assumed that such a restriction does not exist in therespective preceding claims.

It is preferably provided that the pressure sensor supplies adifferential pressure measurement signal and an absolute pressuremeasurement signal as a first and second measurement signal, thedifferential pressure measurement signal representing a differencebetween a pressure in the high-pressure impulse line and a pressure inthe low-pressure impulse line and the absolute pressure measurementsignal a pressure in the high- or low-pressure impulse line,particularly the high-pressure impulse line. It is alternativelyprovided that the pressure sensor supplies a first and a second absolutepressure measurement signal representing the pressure in the high- orlow-pressure impulse line as the first and second measurement signal.

It can also be provided that the pressure sensor supplies, on the basisof the first and second absolute pressure measurement signal, adifferential pressure measurement signal as the first measurement signaland either the first or second absolute pressure measurement signal asthe second measurement signal. This has advantages, on the one hand, inthat only two pressure measurement signals, namely the two absolutepressure measurement signals, are recorded and also in this respect onlytwo sensors are required, and, on the other, because of a furtherincreased accuracy in applying the method because of the dependency ofthe first measurement signal on the second measurement signal if namelythe first measurement signal is a difference between two absolutepressure measurement signals and the second measurement signal is one ofthe two absolute pressure measurement signals.

It is preferably further provided that a cutoff frequency or an dampingor a gain factor or a comparable physical variable or a comparableparameter is determined as the characteristic value. Such characteristicvalues are variables which allow a direct physical interpretation andtherefore facilitate their evaluation. In addition, such characteristicvalues can also be made available to an operator, i.e. displayed, forexample, as absolute variables for his information in addition to anautomatic evaluation by way of comparison with a reference value.

According to an advantageous embodiment of the invention it is providedthat a plurality of characteristic values are determined, wherein, forexample, comparing a first characteristic value with a relevantreference value enables a conclusion to be drawn in respect of a faultin both impulse lines and comparing a second characteristic value with arelevant reference value enables a conclusion to be drawn in respect ofa fault either in one of the two impulse lines or in both impulse lines.By logically combining both conclusions it is then possible to derive aconclusion concerning a fault in one of the two impulse lines. Anexample may explain this: according to the findings of the invention, asthe result of evaluating the damping as characteristic value, aconclusion regarding a blockage in both impulse lines (“both legsblocked” for short) is obtained. In addition, as the result ofevaluating the cutoff frequency as the characteristic value, aconclusion regarding a blockage either in one impulse line or in bothimpulse lines (“one or both legs blocked” for short) is obtained. Bylogically combining the two results, e.g. such that in the result “oneor both legs blocked” all the “both leg blockages” are suppressed, aresult in respect of a blockage on one leg is produced. Such acombination can be implemented by logical ANDing, wherein one of the twoparameters is negated. Evaluation according to this embodiment of theinvention increases the accuracy and/or the informative value of theresults obtainable by the diagnostic method or by means of thecorrespondingly operating transducer.

The claims filed with the application are formulation proposals withoutprejudice to the obtaining of broader patent protection. The Applicantreserves the right to claim additional combinations of features onlydisclosed so far in the description and/or drawings.

The or each exemplary embodiment should not be interpreted as alimitation of the invention. On the contrary, within the scope of thepresent disclosure numerous changes and modifications are possible,especially such variants and, combinations that, for example, as aresult of combinations or modifications of individual features orelements or method steps contained in the general description, in thedescriptions of various embodiments, and in the claims, and illustratedin the drawing, can be comprehended by persons skilled in the art as faras the achievement of the object is concerned and, as a result ofcombinable features, lead to a novel article or to novel method stepsand/or sequences of method steps.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention will now be explained ingreater detail with reference to the accompanying drawings.Corresponding objects or elements are provided with the same referencecharacters in all the figures, in which

FIG. 1 shows a pressure transducer coupled to a pipe through which afluid flows, and

FIG. 2,

FIG. 3 and

FIG. 4 show diagrams for evaluating characteristic values which areproduced from parameters of a model describing a response of thetransducer on the basis of measurement signals recorded by the pressuretransducer.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows, in schematically simplified form, a pressure transducer 14coupled to a pipe 12 through which a fluid 10 flows. The pressuretransducer 14 incorporates, as a sensing element, a pressure sensor 16which is coupled to the pipe 12 by means of a first and a second impulseline, hereinafter referred to as the high- and low-pressure impulse line18, 20, the high-pressure impulse line 18 engaging the pipe 12 e.g.upstream of a point of discontinuity such as a so-called orifice meter22. The low-pressure impulse line 20 engages the pipe 12 accordinglydownstream of the orifice meter 22. It can also be provided that the twoimpulse lines 18, 20 engage the pipe 12 inside an orifice meter havingan orifice plate (not shown). The high-pressure impulse line 18 thenengages the pipe 12 upstream of the orifice plate and the low-pressureimpulse line 20 downstream of the orifice plate.

The pressure sensor 16 delivers at least one measurement signal 24 inrespect of pressure conditions in the region of the orifice meter 22. Itis provided that, in addition to the measurement signal 24—hereinafterreferred to as a first measurement signal 24—a second measurement signal26 is supplied by the pressure sensor 16.

In respect of the first and second measurement signal 24, 26 it isprovided according to alternative, i.e. essentially equivalentembodiments, that the first and second measurement signal 24, 26 iseither a differential pressure measurement signal 24 or an absolutepressure measurement signal 26, the differential pressure measurementsignal 24 representing a difference between a pressure in thehigh-pressure impulse line 18 and a pressure in the low-pressure impulseline 20 and the absolute pressure measurement signal 26 representing thepressure in either the high- or the low-pressure impulse line 18, 20. Inthe alternative embodiment it is provided that the pressure sensor 16supplies, as the first and second measurement signal 24, 26, a first anda second absolute pressure measurement signal 24, 26 representing thepressure in the high- or low-pressure impulse line 18,20.

The first and second measurement signal 24, 26 is fed to an analysisdevice 30 or can be fed to the analysis device 30. The first and secondmeasurement signal 24, 26 is analyzed by the analysis device 30 and atleast one characteristic value 32 characterizing the first and secondmeasurement signal 24, 26 is determined and stored in suitable form,output and/or further processed in a manner known per se. In addition tothe characteristic value 32, the analysis device 30 also administers atleast one predefined or predefinable reference value 34 which is helde.g. in a reference value memory 36 incorporated in the analysis device30. Possibly using comparing means provided for that purpose, such as acomparator 38, the analysis device 30 compares the characteristic value32 with the reference value 34 (or a plurality of characteristic values32 with a reference value 34 or a characteristic value 32 with aplurality of reference values 34 or a plurality of characteristic values32 with a plurality of reference values 34 and, depending on the resultof the comparison, initiates a predefined or predefinable action 40,e.g. outputting of a warning, an output unit 42 or the like possiblybeing provided for issuing such a warning.

Further details concerning the analysis device 30, i.e. functional unitsincorporated therein and functionalities associated therewith, will nowbe explained. According to the embodiment shown in FIG. 1, the analysisdevice 30 comprises a pre-processing unit 44 which, in addition todigitizing the first and second measurement signal 24, 26, for example,is designed to store a predefined or predefinable number of measuredvalues from the two measurement signals 24, 26, the stored measuredvalues being held in a signal memory 46.

For the further description it will be assumed by way of example thatthe pressure sensor 16 supplies, as the first measurement signal 24, adifferential pressure measurement signal 24 and, as the secondmeasurement signal 26, an absolute pressure measurement signal 26relating to the high-pressure impulse line 18. As symbols for these twomeasurement signals 24, 26, the letters d and a respectively are used. Anumber of stored measured values is denoted by N. Used as the basis fordescribing a response of impulse lines 18, 20 is a mathematical model 48which is assigned e.g. to a first functional unit 50 which is designedto determine or estimate parameters of the model 48. In the case of anon-zero second-order model 48 with two poles, as parameters 52 of sucha model 48, the variables P₁, P₂, P₃ are determined from a(i−1), d(i),d(i−1) with e.g. i=1 . . . 20 as sampling instants using the followingrelation:

$\begin{Bmatrix}P_{1} \\P_{2} \\P_{3}\end{Bmatrix} = {\begin{bmatrix}{a^{2}( {i - 1} )} & {{a( {i - 1} )}{a( {i - 2} )}} & {{- {a( {i - 1} )}}{d( {i - 2} )}} \\{{a( {i - 2} )}{a( {i - 1} )}} & {a^{2}( {i - 2} )} & {{- {a( {i - 2} )}}{d( {i - 2} )}} \\{{- {d( {i - 2} )}}{a( {i - 1} )}} & {{- {d( {i - 2} )}}{a( {i - 2} )}} & {d^{2}( {i - 2} )}\end{bmatrix}^{- 1}\begin{Bmatrix}{{- {a(i)}}{a( {i - 1} )}} \\{{- {a(i)}}{a( {i - 2} )}} \\{{a(i)}{d( {i - 2} )}}\end{Bmatrix}}$

According to “Ljung, L.; System Identification—Theory for the User;Prentice Hall, 2^(nd) Edition 1999”, the parameters 52, i.e. thevariables P₁, P₂, P₃, are estimates for the model parameters of alinear, so-called AR model 48, “AR” standing for “autoregressive”. Thelatter is based on the following mathematical description

a(i)+P ₁ a(i−1)+P ₂ a(i−2)=P ₃ d(i−2)

which is the discretized (with sampling time T) form of the followingdescription of the continuous frequency model 48

(−ω²+2ξω_(g) iω+ω ² _(g))A=cD

where A(ω) and D(ω) are the measurement signals 24, 26—a(t),d(t)—transformed to the frequency domain, j the so-called complex unitand ω the signal frequency.

This model 48 results, for example, if one or more variables recorded bythe model 48 may be regarded as subject to an inertia L_(h), a frictioncomponent R_(h) and a compliance C_(h). The variables recorded by themodel 48 include in particular the fluid 10 in the or each impulse line18, 20, the or each impulse line 18, 20, the pressure transducer 14,components incorporated by the pressure transducer 14, such as e.g. theorifice meter 22, etc. These or similar variables are all dependent onthe free diameter and the length of the or each impulse line 18, 20 ormaterial properties of the fluid 10, e.g. density or viscosity.

By means of a second functional unit 54, on the basis of the parameters52 determined by means of the first functional unit 50, one or morecharacteristic values 32 can be determined as a function of themeasurement signals 24, 26. The or each characteristic value 32 isconcretely produced on the basis of the measurement signals 24, 26,because the or each parameter 52 describes the response of the impulselines 18, 20 on the basis of the measurement signals 24, 26 and the oreach characteristic value 32 is produced on the basis of at leastindividual parameters 52.

A physical interpretation can be assigned to the variables

${\omega_{g} = \frac{P_{2} - P_{1} + 1}{T^{2}}},{\xi = {\frac{T}{2}\frac{P_{1} - 2}{P_{2} + 1 - P_{1}}}},{c = P_{3}}$

thereby derived from the parameters 52 as characteristic values 32,namely as cutoff frequency ω_(g), fluid damping in the (respective)impulse line, hereinafter termed damping ξ for short, or gain factor c.

The representation of the pressure transducer 14 shown in FIG. 1 relatesto evaluation of the cutoff frequency ω_(g) as the characteristic value32. The second functional unit 54 is accordingly designed to determinethe cutoff frequency ω_(g). At least one value suitable for evaluatingthe cutoff frequency ω_(g) is provided in the reference value memory 36as the reference value 34.

The cutoff frequency ω_(g) is inversely proportional to a duration of atransfer in the impulse line. This duration is a measure for how long ittakes for a “steady state condition” to become established as the resultof a flow rate change at the pressure transducer 14. For evaluating thecharacteristic value 32 cutoff frequency ω_(g) a limit value for anestimated settling time can be specified which is only just unacceptablefor the relevant application or evaluation case. The settling time or avalue which is derived from the settling time and suitable for directcomparison with the cutoff frequency ω_(g) can accordingly be used asthe reference value 34.

For other characteristic values 32, i.e. damping ξ or gain factor c, forexample, the above statements apply accordingly.

FIG. 2 shows, in the upper diagram, values for the cutoff frequencyω_(g) recorded over time t, the numerical values shown denotingindividual sampling points. To evaluate the relevant values for thecutoff frequency ω_(g) as the characteristic value 32, a reference value34 is provided which is marked on the upper diagram of FIG. 2 as ahorizontal line at the position “145”. Whenever the relevantcharacteristic value 32, i.e. in the case of the diagram in FIG. 2 thecutoff frequency ω_(g), is greater than the relevant reference value 34,i.e. the value of 145, an initial situation in terms of the response ofthe impulse lines 18, 20 is present.

The upper diagram in FIG. 2 is the result of a simulation, the generalconditions of the simulation being specified in the lower diagram ofFIG. 2. For the same time base, the lower diagram in FIG. 2 shows threegraphs 60, 62, 64, an upper graph 60 at a “High level” indicatingblockage of both impulse lines 18, 20 and a lower graph 62 blockage ofthe high-pressure impulse line 18. The blockage either of both impulselines 18, 20 or of the high-pressure impulse line 18 is produced fortest purposes as part of the simulation. The middle graph 64 of FIG. 2shows a result of a possible evaluation on the basis of consideration ofthe cutoff frequency ω_(g). Whenever the middle graph 64 shows a “Highlevel”, evaluation of the cutoff frequency ω_(g) indicates a detectedblockage of at least one impulse line 18, 20 in consideration of therespective reference value 34. On the basis of a comparison of thegraphs 60-64 shown in the lower diagram of FIG. 2 it emerges that eithera blockage of the high-pressure impulse line 18 or a blockage of bothimpulse lines 18, 20 is very clearly identifiable by evaluating thecutoff frequency ω_(g) as the characteristic value 32. Only isolatedmis-evaluations occur, e.g. in the region of t=300, t=2700 and t=3800.

FIG. 3 shows a diagram similar to that in FIG. 2. It differs from thediagram in FIG. 2 in that, in the upper part of FIG. 3, the damping ξ isnow plotted as 2ξω_(g) as the characteristic value 32. Also for such acharacteristic value 32, an associated reference value 34 is providedfor its evaluation. The reference value 34 is marked as a horizontalline at “−290”. The three graphs 60-64 in the lower diagram in FIG. 3again describe (analogously to the conditions already explained inconnection with FIG. 2) the underlying situation according to thesimulation, the upper graph 60 indicating the instants at which bothimpulse lines 18, 20 are blocked and the lower graph 62 indicating theinstants at which the high-pressure impulse line 18 is blocked. Themiddle graph 64 indicates when, on the basis of an evaluation of thedamping ξ as the limit value 32, blockage is detected in considerationof the underlying reference value 34 at “−290”. Because of using Nmeasured values, detection takes place, as also in FIG. 2, in a somewhattime-delayed manner. As is also the case in the diagram in FIG. 2, thereare a shall number of positions at which mis-evaluations occur on thebasis of evaluating the damping ξ as the characteristic value 32. Thisis the case in the situation shown, e.g. in the region of t=2000 andt=3400.

FIG. 4 shows a diagram similar to those shown in FIG. 2 and FIG. 3 onthe same time base. The diagram in FIG. 4 relates to an evaluation ofthe gain factor c as the characteristic value 32. The characteristicvalue 32 is assigned, as the reference value 34, the numerical value“5×10⁶”. The lower diagram in FIG. 4 describes the underlying conditionsgenerated in the simulation, i.e. on the basis of the upper graph 60instants at which both impulse lines 18, 20 are blocked, and on thebasis of the lower graph 62 instants at which the high-pressure impulseline 18 is blocked. The middle graph 64 again indicates the result ofthe evaluation of the gain factors c as the characteristic value 32. Asmall number of mis-evaluations also occur in this evaluation, e.g. inthe region of t=300, t=600, t=900, t=2300, t=3600 and t=3700.

Evaluation of the damping ξ as the characteristic value 32 produces aresult indicating that both impulse lines 18, 20 are blocked (see FIG.3). Evaluation of the cutoff frequency ω_(g) as the characteristic value32 (see FIG. 2) produces a result indicating either both legs blocked orone leg blocked, i.e. blockage of the high-pressure impulse line 18 inthe case of an absolute pressure signal 26 relating to the high-pressureimpulse line 18. By logically combining the result “both legs blocked”of the evaluation according to FIG. 2 with the result “both legs or oneleg blocked” of the evaluation according to FIG. 3, a result indicatinga single leg blocked condition can be obtained.

A corresponding result can be obtained if, instead of the result of theevaluation according to FIG. 2, the result of the evaluation accordingto FIG. 4, which likewise indicates both legs or one leg blocked,together with an evaluation of the situation according to FIG. 3 is usedas the basis.

The invention may therefore be summarized as follows: a method fordetecting or diagnosing an impulse line blockage in a pressuretransducer 14 and a corresponding pressure transducer 14 are specified,wherein to analyze at least one measurement signal 24, 26 at least onecharacteristic value 32 is compared with at least one reference value 34and, depending on the result of the comparison, an action 40 isinitiated, the or each characteristic value 32 being produced on thebasis of at least individual parameters 52 of a model 48 describing aresponse of impulse lines 18, 20 by which the pressure transducer 14 iscoupled to a pipe 12 through which a fluid 10 flows.

1.-9. (canceled)
 10. A method for operating a pressure transducer whichis connected to a pipe at least by a high-pressure and a low-pressureimpulse line, comprising: supplying a first measurement signal and asecond measurement signal by a pressure sensor incorporated by thepressure transducer; determining a characteristic value in relation tothe first and second measurement signal by an analysis device, whereinparameters of a model describing a response of the high-pressure and thelow-pressure impulse lines are determined based upon the first andsecond measurement signal and the characteristic value is produced basedupon individual parameters; comparing the characteristic value with apredefined reference value by the analysis device; and initiating apredefined action depending on the result of the comparison by theanalysis device.
 11. The method as claimed in claim 10, wherein thepressure sensor supplies a differential pressure measurement signal asthe first measurement signal and an absolute pressure measurement signalas the second measurement signal, the differential pressure measurementsignal representing a difference between a pressure in the high-pressureimpulse line and a pressure in the low-pressure impulse line and theabsolute pressure measurement signal representing the pressure in thehigh- or low-pressure impulse line.
 12. The method as claimed in claim10, wherein the pressure sensor supplies a first and a second absolutepressure measurement signal as the first and second measurement signalwhich represent a pressure in the high-pressure impulse line and thelow-pressure impulse line respectively.
 13. The method as claimed inclaim 12, wherein the pressure sensor supplies a differential pressuremeasurement signal as the first measurement signal and either the firstor second absolute pressure measurement signal as the second measurementsignal.
 14. The method as claimed in claim 10, wherein a cutofffrequency or a damping or a gain factor is determined as thecharacteristic value.
 15. The method as claimed in claim 11, wherein acutoff frequency or a damping or a gain factor is determined as thecharacteristic value.
 16. The method as claimed in claim 12, wherein acutoff frequency or a damping or a gain factor is determined as thecharacteristic value.
 17. The method as claimed in claim 14, wherein aplurality of characteristic values are determined, a comparison of afirst characteristic value with a respective reference value enabling aconclusion to be drawn in respect of a fault in both impulse lines and acomparison of a second characteristic value with a respective referencevalue enabling a conclusion to be drawn in respect of a fault either inone of the two impulse lines or in both impulse lines, wherein a logicalcombination of both conclusions produces a conclusion concerning a faultin one of the two impulse lines.
 18. A pressure transducer connected toa pipe by at least one high- and low-pressure impulse line, comprising:a pressure sensor for delivering a first measurement signal and a secondmeasurement signal; and an analysis device for determining acharacteristic value relating to the first and second measurementsignal, wherein parameters of a model describing a response of thehigh-pressure and the low-pressure impulse lines are determined by theanalysis device based upon the first and second measurement signal, andwherein the characteristic value is produced based upon individualparameters, comparing the characteristic value with a predefinedreference value, and initiating a predefined action depending on theresult of the comparison.
 19. The pressure transducer as claimed inclaim 18, wherein the pressure sensor supplies a differential pressuremeasurement signal as the first measurement signal and an absolutepressure measurement signal as the second measurement signal, thedifferential pressure measurement signal representing a differencebetween a pressure in the high-pressure impulse line and a pressure inthe low-pressure impulse line and the absolute pressure measurementsignal representing the pressure in the high- or low-pressure impulseline.
 20. The pressure transducer as claimed in claim 18, wherein thepressure sensor supplies a first and a second absolute pressuremeasurement signal as the first and second measurement signal whichrepresent a pressure in the high-pressure impulse line and thelow-pressure impulse line respectively.
 21. The pressure transducer asclaimed in claim 20, wherein the pressure sensor supplies a differentialpressure measurement signal as the first measurement signal and eitherthe first or second absolute pressure measurement signal as the secondmeasurement signal.
 22. The pressure transducer as claimed in claim 18,wherein a cutoff frequency or a damping or a gain factor is determinedas the characteristic value.
 23. The pressure transducer as claimed inclaim 22, wherein a plurality of characteristic values are determined, acomparison of a first characteristic value with a respective referencevalue enabling a conclusion to be drawn in respect of a fault in bothimpulse lines and a comparison of a second characteristic value with arespective reference value enabling a conclusion to be drawn in respectof a fault either in one of the two impulse lines or in both impulselines, wherein a logical combination of both conclusions produces aconclusion concerning a fault in one of the two impulse lines.
 24. Acomputer readable medium storing a computer program withcomputer-executable program code instructions which, when executed on acomputer system, perform a method, comprising: supplying a firstmeasurement signal and a second measurement signal by a pressure sensorincorporated by a pressure transducer which is connected to a pipe atleast by a high-pressure and a low-pressure impulse line; determining acharacteristic value in relation to the first and second measurementsignal by an analysis device, wherein parameters of a model describing aresponse of the high-pressure and the low-pressure impulse lines aredetermined based upon the first and second measurement signal and thatthe characteristic value is produced based upon individual parameters;comparing the characteristic value with a predefined reference value bythe analysis device; and initiating a predefined action depending on theresult of the comparison by the analysis device.
 25. The computerreadable medium as claimed in claim 24, wherein the pressure sensorsupplies a differential pressure measurement signal as the firstmeasurement signal and an absolute pressure measurement signal as thesecond measurement signal, the differential pressure measurement signalrepresenting a difference between a pressure in the high-pressureimpulse line and a pressure in the low-pressure impulse line and theabsolute pressure measurement signal representing the pressure in thehigh- or low-pressure impulse line.
 26. The computer readable medium asclaimed in claim 24, wherein the pressure sensor supplies a first and asecond absolute pressure measurement signal as the first and secondmeasurement signal which represent a pressure in the high-pressureimpulse line and the low-pressure impulse line respectively.
 27. Thecomputer readable medium as claimed in claim 26, wherein the pressuresensor supplies a differential pressure measurement signal as the firstmeasurement signal and either the first or second absolute pressuremeasurement signal as the second measurement signal.
 28. The computerreadable medium as claimed in claim 24, wherein a cutoff frequency or adamping or a gain factor is determined as the characteristic value. 29.The computer readable medium as claimed in claim 28, wherein a pluralityof characteristic values are determined, a comparison of a firstcharacteristic value with a respective reference value enabling aconclusion to be drawn in respect of a fault in both impulse lines and acomparison of a second characteristic value with a respective referencevalue enabling a conclusion to be drawn in respect of a fault either inone of the two impulse lines or in both impulse lines, wherein a logicalcombination of both conclusions produces a conclusion concerning a faultin one of the two impulse lines.